2012年6月27日 星期三

Viewing Images of High-Calorie Foods Brings On High-Calorie Cravings, Research Finds


Viewing Images of High-Calorie Foods Brings On High-Calorie Cravings, Research Finds

ScienceDaily (June 25, 2012) — You're minding your own business when a food craving suddenly hits, and if you just saw an image of a cupcake, or consumed a sugary soda, that may be no accident.
Researchers at the University of Southern California (USC) will present preliminary findings June 26 at the Endocrine Society's annual meeting demonstrating that viewing pictures of high-fat foods and drinking sweetened beverages while viewing the pictures stimulate appetite and reward centers in the brain.
"Studies have shown that advertisements featuring food make us think of eating, but our research looked at how the brain responds to food cues and how that increases hunger and desire for certain foods," said Kathleen Page, principal investigator and assistant professor of clinical medicine at the Keck School of Medicine of USC. "This stimulation of the brain's reward areas may contribute to overeating and obesity, and has important public health implications."
Page's presentation, "Fructose Compared to Glucose Ingestion Preferentially Activates Brain Reward Regions in Response to High-Calorie Food Cues in Young, Obese Hispanic Females," will be made on June 26, during the Endocrine Society meeting, which takes place from July 23 to 26 in Houston, Texas.
Page and colleagues used functional magnetic resonance imaging (fMRI) to measure the brain responses of 13 obese, Hispanic adolescent women ranging in age from 15 to 25. Women were chosen because prior research indicates they are more responsive to food cues; the study group was narrowed to Hispanic women because of the high risk of obesity and type 2 diabetes in the Hispanic community.
The women's brain responses were scanned twice as they looked at pictures of high-calorie foods, such as hamburgers, cookies, and cakes, and low-calorie foods such as fruits and vegetables. After seeing the high-calorie and low-calorie groupings, the participants rated their hunger and desire for sweet or savory foods on a scale from one to 10.
Halfway through the scans, the women drank 50 grams of glucose -- equivalent to a can of soda -- and another time, they drank 50 grams of fructose. Glucose and fructose are the main components of table sugar and high-fructose corn syrup.
"We hypothesized that the reward areas in the women's brains would be activated when they were looking at high-calorie foods, and that did happen," said Page. "What we didn't expect was that consuming the glucose and fructose would increase their hunger and desire for savory foods."
The researchers also noted that fructose stimulated more hunger and desire in the participants' brains than glucose did.
"Our bodies are made to eat food and store energy, and in prehistoric days, it behooved us to eat a lot of high-calorie foods because we didn't know when the next meal was coming," Page said. "But now we have much more access to food, and this research indicates added sweeteners might be affecting our desire for it."
With many questions unanswered about whether these cravings are environmental (caused by obesity) or genetic, Page plans to study what happens to the brains of obese individuals while they are dieting.
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Hormone, Oxytocin, Shows Potential as Weight-Loss Treatment


Hormone, Oxytocin, Shows Potential as Weight-Loss Treatment

ScienceDaily (June 25, 2012) — A reproductive hormone helps regulate food intake and energy metabolism without causing adverse effects, a new animal study finds. The results were presented June 25 at The Endocrine Society's 94th Annual Meeting in Houston.
Secreted by the brain, the neural hormone, oxytocin, helps initiate contractions of the uterus and breast-milk-producing glands during childbirth and nursing. Prior research by lead author Yuko Maejima, Ph.D., and her co-investigators also linked oxytocin to the process of controlling energy intake and use.
"These findings reveal novel anti-obese and anti-metabolic-syndrome effects of oxytocin," said Maejima, who also is an assistant professor in the physiology department at Jichi Medical University in Shimotsuke, Tochigi, Japan. "Thus, our results provide an avenue for developing an oxytocin-based effective and safe treatment of obesity."
Excess weight is a risk factor for numerous diseases, including diabetes, heart and blood-vessel disease, and cancer, and is a major problem throughout the world. Obesity rates have more than doubled since 1980, according to statistics from the World Health Organization, which indicate that more than 1.4 billion adults are overweight and upwards of 500 million are obese.
In an obese animal model, the investigators found that daily injections of oxytocin reduced the amount of food the animals consumed, as well as decreased their body weight during, and for nine days after, treatment.
Similar results were observed with oxytocin administered by implanted mini pumps. This drug-delivery method also reduced fat in the liver, improved glucose tolerance, and decreased abdominal fat, which is a major risk factor for heart and blood-vessel, or cardiovascular disease. Additionally, the mini pumps decreased the size of fat-storage cells, or adipocytes, but did not adversely affect blood pressure or activity levels.
"The finding that peripheral oxytocin treatment has no effect on the normal blood-pressure levels or the locomotor activity of this mouse model suggests that oxytocin may not influence the cardiovascular system or emotions," Maejima said.
To induce obesity, investigators first fed the animal model a high-fat diet. They then administered oxytocin via injection for 17 days, and through the implantable mini pumps for 13 days.
Funding for this study came from: The Ministry of Education, Culture, Sports, Science and Technology of Japan; The Ichiro Kanehara Foundation; Suzuken Memorial Foundation; Itoe Okamoto scientific award SHISEIKAI; Mochida Memorial Foundation for Medical and Pharmaceutical Research; Japan Society for the Promotion of Science; and Takeda Science Foundation.
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Low Vitamin D Levels Linked to Weight Gain in Some Older Women


Low Vitamin D Levels Linked to Weight Gain in Some Older Women

ScienceDaily (June 25, 2012) — Older women with insufficient levels of vitamin D gained more weight than those with sufficient levels of the vitamin, according to a new study funded by the National Institutes of Health and published online June 25 in the Journal of Women's Health. The study of more than 4,600 women ages 65 and older found that over nearly five years, those with insufficient levels of vitamin D in their blood gained about two pounds more than those with adequate levels of the vitamin.
"This is one of the first studies to show that women with low levels of vitamin D gain more weight, and although it was only two pounds, over time that can add up," said study author Erin LeBlanc, MD, an endocrinologist and researcher at the Kaiser Permanente Center for Health Research in Portland, Ore. "Nearly 80 percent of women in our study had insufficient levels of vitamin D. A primary source of this important vitamin is sunlight, and as modern societies move indoors, continuous vitamin D insufficiency may be contributing to chronic weight gain."
Vitamin D was in the news recently when a panel of primary care experts -- the US Preventive Services Task Force -- said healthy postmenopausal women may need higher doses of the vitamin to prevent fractures, and that there isn't enough evidence to recommend the supplements for younger people. Other expert groups, including the Endocrine Society, have a different take, saying many adults do need vitamin D supplements to keep their bones healthy. 1
"Our study only shows an association between insufficient levels of vitamin D and weight gain, we would need to do more studies before recommending the supplements to keep people from gaining weight," Dr. LeBlanc said. "Since there are so many conflicting recommendations about taking vitamin D for any reason, it's best if patients get advice from their own health care provider."
She points out that this study was conducted among older women who, for the most part, were not trying to lose weight -- though some of them did so as a natural result of aging. About 60 percent of the 4,659 women in the study remained at a stable weight (within 5 percent of their starting weight) over the 4.5-year study period, 27 percent lost more than 5 percent of their body weight, and 12 percent gained more than 5 percent of their body weight.
Most women in the study (78 percent) had less than 30 nanograms per millimeter (ng/ml) of vitamin D in their blood -- the level defined as sufficient by the Endocrine Society panel of experts who set clinical guidelines on vitamin D deficiency (pdf). These women had higher baseline weight to begin with: 148.6 pounds, compared with 141.6 pounds for women whose vitamin D levels were 30 ng/ml or above. Insufficient levels had no association with weight changes in the entire group of women, or in the group that lost weight. But in the group of 571 women who gained weight, those with insufficient vitamin D levels gained more -- 18.5 pounds over five years -- than women who had sufficient vitamin D. The latter group gained 16.4 pounds over the same period.
This study is part of a larger project called the Study of Osteoporotic Fractures that has been ongoing for more than two decades. During 1986-88, SOF enrolled nearly 10,000 women ages 65 and older and tracked their medical history through office and home visits, mailed surveys and telephone calls. The women are from Baltimore, Minneapolis, Portland, Ore. and the Monongahela Valley near Pittsburgh. The SOF study is supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the National Institute on Aging.
Authors include Erin S. LeBlanc, MD, MPH, Joanne H. Rizzo, MPA, Kathryn L. Pedula and Teresa A. Hillier, MD, from the Kaiser Permanente Center for Health Research in Portland, Ore.; Kristine E. Ensrud, MD, from the Veterans Affairs Medical Center and Department of Medicine and Division of Epidemiology & Community Health, University of Minnesota in St. Paul; Jane Cauley, MD, Department of Epidemiology, University of Pittsburgh; and Marc Hochberg, MD, from the Department of Medicine, University of Maryland in Baltimore.
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Experimental Drug Helps Diabetes Patients Lose Weight


Experimental Drug Helps Diabetes Patients Lose Weight

ScienceDaily (June 25, 2012) — An experimental drug helped significantly more overweight patients with diabetes shed pounds, compared with placebo, a new study finds. The results were presented June 23 at The Endocrine Society's 94th Annual Meeting in Houston.
"This new medication is promising because of the amount of weight loss it produces, the resultant improvement in important risk factors for diabetes, and, particularly in the lower dose studied, in its tolerability," said study lead author Donna H. Ryan, M.D., professor emeritus at Pennington Biomedical Research Center (LSU System) in Baton Rouge, LA.
Diabetes treatment involves weight management and medications to control blood-sugar levels and risk factors. If left untreated, diabetes can increase the danger of developing heart and blood-vessel diseases. Since one of the main risk factors for all of these diseases is obesity, weight loss is important to both prevention and treatment.
Focusing on type 2 diabetes, investigators found that patients who took the experimental weight-loss drug phentermine/topiramate, combined with diet and exercise modifications, were more likely to lose moderate amounts of weight than those who received a sugar-pill placebo and the diet and exercise intervention.
The percentage of study participants losing more than 10 percent of their initial weight while decreasing their blood pressure and hemoglobin A1c, was:
• 14 percent on low-dose phentermine/topiramate
• 31 percent on high-dose phentermine/topiramate
• 4 percent on placebo
Phentermine/topiramate is a combined medication that works by decreasing appetite. The main side effects associated with the drug were constipation and tingling sensations in the fingers. Patients who took phentermine/topiramate were also more likely to develop low blood sugar than those who received placebo.
This study was an analysis of diabetic patients who enrolled in weight-loss studies testing medications given with lifestyle intervention. Investigators randomly assigned 357 patients with type 2 diabetes to receive either low-dose phentermine/topiramate (7.5 milligrams), high-dose phentermine/topiramate (15 milligrams), or placebo. Neither investigators nor patients knew who was receiving the drug versus placebo in the double-blinded study. Participants' average age was 53 years, 66 percent were female, most were white, and their average weight was 222 pounds. Follow-up was one year.
VIVUS, the company that developed phentermine/topiramate, funded the study.
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'Dessert With Breakfast Diet' Helps Avoid Weight Regain by Reducing Cravings


'Dessert With Breakfast Diet' Helps Avoid Weight Regain by Reducing Cravings

ScienceDaily (June 25, 2012) — Dieters have less hunger and cravings throughout the day and are better able to keep off lost weight if they eat a carbohydrate-rich, protein-packed breakfast that includes dessert. These findings come from a new study that was presented June 25 at The Endocrine Society's 94th Annual Meeting in Houston.
"The goal of a weight loss diet should be not only weight reduction but also reduction of hunger and cravings, thus helping prevent weight regain," said Daniela Jakubowicz, MD, the study's principal investigator.
Jakubowicz, a senior physician at Tel Aviv University's Wolfson Medical Center in Holon, Israel, and her co-authors studied nearly 200 nondiabetic obese adults who were randomly assigned to eat one of two low-calorie diets. Both diets had the same number of daily calories -- about 1,600 for men and 1,400 for women -- but differed mainly in the composition of breakfast.
One group received a low-carbohydrate diet, featuring a 304-calorie breakfast with only 10 grams of carbohydrates, or "carbs." The other group ate a 600-calorie breakfast with 60 grams of carbs, which included a small sweet, such as chocolate, a doughnut, a cookie or cake. Both diets contained protein (such as tuna, egg whites, cheese and low-fat milk) at breakfast, but the "dessert with breakfast diet" had 45 grams of protein, 15 grams more than in the low-carb diet.
Halfway through the eight-month study, participants in both groups lost an average of 33 pounds (15.1 kilograms, or kg) per person, which Jakubowicz said shows that "both diets work the same." However, in the last four months of the study, the low-carb group regained an average of 22 pounds (11.6 kg) per person, while participants who ate the dessert with breakfast diet lost another 15 pounds (6.9 kg) each, the authors reported.
In addition, the study subjects who ate the dessert with breakfast diet reported feeling less hunger and fewer cravings compared with the other group. Subjects' food diaries showed that the dessert with breakfast group had better compliance in sticking to their calorie requirements. Women who ate the dessert with breakfast diet were allowed 500 calories for lunch and about 300 calories for dinner. Men in that group could eat a 600-calorie lunch and up to 464 calories at dinner.
As further evidence supporting the dessert with breakfast diet, the levels of ghrelin, the so-called "hunger hormone," dropped much more after breakfast than in the low-carb group: 45.2 percent versus 29.5 percent, respectively, according to the abstract.
Jakubowicz attributed the better results from the dessert with breakfast diet to meal timing and composition. She said the diet's high protein content reduced hunger; the combination of protein and carbs increased satiety, or feeling full; and the dessert decreased cravings for sweet, starchy and fatty foods. Such cravings often occur when a diet restricts sweets and can result in eating many fattening foods that are not allowed on the diet, she said.
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Ratio of Appetite-Regulating Hormones Marker of Successful Dieters


Ratio of Appetite-Regulating Hormones Marker of Successful Dieters

ScienceDaily (June 25, 2012) — A pre-diet measurement of two hormones related to weight regulation can help predict which dieters will be more likely to maintain their weight loss and who will not, according to a new study. The results were presented June 24 at The Endocrine Society's 94th Annual Meeting in Houston.
With obesity rates in many countries steadily climbing, more people are turning to diets to lose weight. But, for many people, maintaining the weight loss can be extremely difficult, leading to a frustrating cycle of weight loss and gain.
"The current study shows for the first time a clinically useful marker to identify, at an early time, patients who have difficulties in maintaining their body weight," said study author Ana B. Crujeiras , Ph.D., doctor at University Hospital of Santiago de Compostela (CHUS) and Biomedical Network Research Center in Physiopathology of obesity and Nutrition (CIBERobn) in Santiago de Compestela, Spain. "This difficulty is one of the most significant obstacles for obesity therapy, and currently there are no biological markers that effectively demonstrate clinical usefulness in predicting weight-loss regain."
To address this problem, investigators analyzed the role of two hormones related to appetite regulation. Leptin is made by the cells found in fat tissue, and ghrelin is mainly manufactured by cells in the stomach. Previous research by Crujeiras and co-investigators showed that patients who later regained weight had higher leptin and lower ghrelin levels before starting a restricted-calorie diet.
In the current study, investigators found the pre-diet leptin/ghrelin ratio to be two times higher among study participants who later regained weight than among those who did not. Additionally, they identified cut-off points, which predicted more than 60 percent of patients who would later regain 10 percent or more of the weight they initially lost.
"Calculating the leptin/ghrelin ratio prior to the participation in a weight-reduction program might provide the opportunity to individualize weight-loss therapeutic programs according to patients' needs, counteracting the weight-regain rate, and, as a consequence, achieving successful management of obesity," Crujeiras said.
Among women, the leptin/ghrelin ratio identified 70 percent of participants who later regained weight. Among men, the rate was even higher at 95 percent. Women, however, were less likely than men to be incorrectly identified as future weight gainers.
Eighty-eight overweight or obese patients, with a body mass index greater than 25, enrolled in the eight-week study. They were 44 percent female, their average age was 35 years, and all were white.
After an initial fast, participants' blood levels of leptin and ghrelin were measured. They then followed a reduced calorie diet for eight weeks. At the six-month follow-up, 40 dieters had regained the weight they had lost, while the remaining 48 had not. The Biomedical Network Research Centre in Physiopathology of obesity and Nutrition (CIBERobn), Institute of Health Carlos III (ISCIII), Spanish Ministry of Economy and Competitiveness; Galician Research, Development and Technological Innovation plan (INCITE), Galician Ministry for Innovation and Industry; and Special Research about Nutrition, Obesity and Health, University of Navarra funded the study.
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Secondhand Smoke Is Linked to Type 2 Diabetes and Obesity


Secondhand Smoke Is Linked to Type 2 Diabetes and Obesity

ScienceDaily (June 25, 2012) — Adults who are exposed to secondhand smoke have higher rates of obesity and Type 2 diabetes than do nonsmokers without environmental exposure to tobacco smoke, a new study shows. The results were presented June 24 at The Endocrine Society's 94th Annual Meeting in Houston.
"More effort needs to be made to reduce exposure of individuals to secondhand smoke," said study co-author Theodore C. Friedman, MD, PhD, chairman of the Department of Internal Medicine at Charles R. Drew University, Los Angeles.
Studies have shown an association between cigarette smoking and an increased rate of Type 2 diabetes despite the fact that most smokers are leaner than nonsmokers and obesity is a risk factor for Type 2 diabetes. Although some studies have suggested a relationship between Type 2 diabetes and passive, or secondhand, smoking, Friedman said these studies have not verified exposure to secondhand smoke through serum (blood) levels of cotinine. Cotinine is a metabolite of nicotine, and serum cotinine measures a person's exposure to tobacco smoke.
In their current study, Friedman and his fellow researchers used serum cotinine levels to verify passive smoking. They examined data from more than 6,300 adults who participated from 2001 to 2006 in the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the U.S. population.
The investigators defined current smokers, which made up 25 percent of the sample, as survey participants who reported that they smoke cigarettes and who had a measured serum cotinine level greater than 3 nanograms per milliliter (ng/mL). Nonsmokers (41 percent of the sample) were those who answered "no" to the question "Do you smoke cigarettes?" and who had a cotinine level below 0.05 ng/mL. Participants who answered "no" to this question but whose cotinine level was above 0.05 ng/mL were defined as secondhand "smokers" (34 percent).
In analyzing these groups, the researchers controlled for age, sex, race, alcohol consumption and physical activity. They found that, compared with nonsmokers, secondhand smokers had a higher measure of insulin resistance, a condition that can lead to Type 2 diabetes; higher levels of fasting blood glucose, or blood sugar; and a higher hemoglobin A1c, a measure of blood sugar control over the past three months.
Secondhand smokers also had a higher rate of Type 2 diabetes, as defined by a hemoglobin A1c greater than 6.5 percent. Secondhand smokers had a similar rate of diabetes to that of current smokers, according to Friedman.
Secondhand smokers also had a higher body mass index (BMI), a measure of body fat, compared with nonsmokers, Friedman reported. Current smokers had a lower BMI than nonsmokers but a higher hemoglobin A1c. When the researchers controlled for BMI, they found that secondhand smokers and current smokers still had a higher hemoglobin A1c than did nonsmokers.
"This finding shows that the association between secondhand smoke and Type 2 diabetes was not due to obesity," Friedman said. "More studies are needed to show whether secondhand smoke is a cause of diabetes."
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